Battery voltage measurement system

Abstract

In one embodiment of the present invention, a system is provided or measuring the voltages of the traction batteries of an electric vehicle. The system includes switches provided to switchably couple the batteries individually to an amplifier. The system also includes switches provided to assure that the same polarity is always provided to the amplifier; a single-ended amplifier can thus be used. The system includes an analog-to-digital converter coupled in communication with the output of the amplifier, and an optical coupler which couples the output of the analog-to-digital converter to the low-voltage portion of the electric vehicle's electrical system.

What is claimed is: 
     
       1. In an electrical system having a high-voltage portion and a low-voltage portion, said high-voltage portion comprising a plurality of series-connected batteries, each with two terminals, said high-voltage portion further isolated by design from said low-voltage portion, a battery voltage measurement system comprising: first and second electrical junctions;   switching means in electrical communication with each battery, said switching means comprising a first switch with a first side and a second side, said first side coupled in electrical communication with a terminal of said battery and said second side coupled in electrical communication with said first junction; and a second switch with a first side and a second side, said first side coupled in electrical communication with the other terminal of said battery and said second side coupled in electrical communication with said second junction;   an amplifier comprising an input terminal, an output terminal and another terminal;   a third switch coupling said amplifier input to said first junction;   a fourth switch coupling said amplifier input to said second junction;   a fifth switch coupling said another terminal to said first junction; and   a sixth switch coupling said another terminal to said second junction;   an analog-to-digital converter located in said high-voltage portion of said system and coupled to receive a signal from the output of said amplifier; and   voltage isolation means coupled between said analog-to-digital converter and said low-voltage portion of said electrical system.   
     
     
       2. A battery voltage measurement system as recited in claim 1, wherein said another terminal is a reference terminal of said amplifier. 
     
     
       3. A battery voltage measurement system as recited in claim 2, wherein said switching means comprises a series connection of field-effect transistors. 
     
     
       4. A battery voltage measurement system as recited in claim 3, wherein said voltage isolation means comprises an optical isolator. 
     
     
       5. A battery voltage measurement system as recited in claim 2, wherein said switching means comprises an electromechanical relay. 
     
     
       6. A battery voltage measurement system as recited in claim 5, wherein said voltage isolation means comprises an optical isolator.